A continuous, worldwide expansion of the air transportation industry has been accompanied by the development of concomitant improvements in performance, range, and capacities of aircraft. In conjunction with this expansion, ground based support systems including radar and navigational facilities for in flight control and the like have been enhanced. Expansion in this industry also has generated substantially enlarged airport facilities with heightened levels of air traffic control. A typical airport facility will have multiple runways with feeding taxiways, runway turn-off lanes, cross-over taxiways extending between runways, and like ground movement support facilities. All such components of the airport complex function in conjunction with passenger and cargo terminals generally disposed over an extensive territorial region. Tower based air controllers thus not only are called upon to monitor and control local airborne traffic engaged in take-off and landing activities, but also to carry out control over what are becoming elaborate traffic patterns of aircraft and airport staff vehicles moving on the ground about the airport complex. A continuing occurrence of collisions between aircraft during ground maneuvering operations has demonstrated a need for a system for the efficient, reliable, and safe control and coordination of aircraft ground traffic. Currently, this coordination by tower based personnel can be drastically hampered by poor visibility, on-airport obstructions, or misidentification of on-airport vehicles.
Human vision of ground traffic by tower personnel currently represents the principal mode of ground movement control, however, this elementary approach is supplemented by the corresponding but highly restricted vision of aircraft pilots, whose vision is essentially forwardly of typically large aircraft, which in a ground movement mode are quite cumbersome. The pilot also will have on board runway-taxiway maps as an aid, for example those distributed by Jeppsen Sanderson, Inc. (Jeppsen Maps). However, such information, while essential, is passive in nature. Where ground visibility is hindered, the pilot can identify aircraft location by radio communication, i.e. cockpit-generated position reports to the tower. That pilot awareness information may be wholly or partially inaccurate. For example, the tail region of larger aircraft may extend into a runway at a cross-over location even though the forward cabin is on the taxiway. Further, with the advent of "hub" inspired traffic, extensive cuing of aircraft now appears at runway thresholds at popular flight times. A misdescription of the aircraft sequence well may impose a human factor's demand upon the working memories of tower personnel which may be the occasion of human error.
Tower based visual perception may be supported through the use of radar, however, radar identification of ground traffic is subject to somewhat inherent constraints. That mode of identification is subject to attenuation by rain or similarly inclement conditions, unfortunately conditions where aircraft position information is most essential. Additionally, radar conventionally exhibits a lack of short range precision and is blocked by ground obstructions and the like. The radar identification approach also will not provide precise aircraft identification but only the presence or absence of a target at any given location without orientation information or the like.